This invention is concerned with suction pick-up apparatus for electrical or electronic components. Such apparatus is used in component placement machines for placing components of varying sizes on a suitable substrate, for example a printed circuit board. Such apparatus comprises one or more pick-up heads movable between a location at which they pick-up a component by suction and a location at which they release the component on to the substrate. Such pick-up heads have pick-up surfaces against which the component is held and for accurate placement it is essential that the size of the pick-up surface at least approximately corresponds to the size of the component. If the pick-up surface is too small the placement force cannot be uniformly applied thereto by the head and the component may tip. If, on the other hand, the pick-up surface is too large, the component cannot be readily centred on the surface and the size of the pick-up surface may restrict access to parts of the substrate because of the possibility of fouling already placed components.
In order to match the pick-up surface to the component, pick-up heads have been constructed with replaceable tips. A magazine of tips with pick-up surfaces of different sizes is provided and, when a component of a different size is to be placed, the pick-up head is moved to the magazine and a tip exchange takes place. This reduces the productivity of the machine. It is also possible to utilise a plurality of alternative pick-up heads each with a different size of pick-up surface but this would be expensive and complex.
The specification of GB Patent Application No. 8702618 describes a suction pick-up apparatus in which pairs of alternative pick-up heads are mounted on carriers spaced around a carousel. The carousel turns to bring the carriers to component pick-up and placement locations and the carriers can be moved relative to the carousel to bring either of the alternative pick-up heads into operation. The pick-up heads on each carrier each have two alternative pick-up surfaces. A first pick-up surface is formed on a body of the pick-up head and a second pick-up surface is formed on a piston member which can project beyond the body or can be retracted into a cylinder within the body. The piston member is retracted when vacuum is applied to the cylinder and projects when air under pressure is applied thereto. It has been found that substantially all the components it is desired to place can be placed using one or other of the pick-up surfaces of one pick-up or other of the pick-up heads.
It is an object of the present invention to provide a pick-up head which can pick-up and place substantially all the components required to be placed in a placement machine without requiring tip exchanges.